This paper proposes a novel control approach for single phase active power filter (APF) based on switched system theory, since the switching performance of APF. The switched model of APF is established by means of switching function. On this basis, the switched system error model is obtained. After that, a quadratic Lyapunov function is design to determine the switched control law. The switched control can make the switched system asymptotically stable and compensate the distorted current caused by the nonlinear load current. The effectiveness and rationality of the proposed approach is confirmed by the simulation result compared with the linear voltage control approach.